I originally posted below, but was informed to suggest the feature here.
In short It’d be great to be able to carve out caves using the terrain system. Things like caves and overhangs are traditionally done with 3rd models, but that’s a complete pain and with todays technology it blows my mind we don’t have a decent terrain system that can do this.
The most practical approach is probably voxel volumes, which is a volume of terrain that behaves like voxels. Other suggests on how to do this with a terrain system are gladly welcomed.